1. Field of the Invention
The invention relates to a method for determining an actuating position of a parking brake in a motor vehicle and to a computer program for performing said method. The invention also relates to a corresponding controller for a parking lock device and the corresponding parking brake system.
2. Description of the Related Art
EP 1 855 033 B1 discloses a transmission lock for a motor vehicle, which serves as a parking lock arrangement. The transmission lock comprises a ratchet wheel that is equipped with teeth in which a pawl engages in a blocked state. The pawl can be actuated by a locking cone that is mounted on a locking element in an axially mobile manner and is pretensioned.
DE 10 2012 205 576 A1 discloses a method for providing a clamping force that is exerted by an auxiliary brake in a motor vehicle. The auxiliary brake has an electric braking motor, by which a brake piston is actuated via a spindle and pushes against a brake disc. In order to determine the clamping force, a motor constant is determined from the voltage and current strength at the braking motor in a no-load phase. A temporal gradient of the current strength at the braking motor is captured to identify the no-load phase. A current strength below followed by a current strength above a first and a second threshold value respectively indicates the start of the no-load phase. The current strength is constant in the no-load phase itself. A subsequent positive gradient in the current strength indicates the end of the no-load phase.
DE 10 2012 206 226 A1 discloses a method for adjusting an auxiliary brake in a vehicle, where a clamping force is exerted on a brake disc via a braking motor. A voltage jump is captured when the braking motor starts up, and a corrected current strength is determined therefrom. The corrected current strength is used as a basis for calculating a motor constant by which the clamping force generated by the auxiliary brake can be determined.
The conventional methods require extensive data relating to the structure of the parking brake or auxiliary brake, and can no longer be used reliably if there is a failure in the vehicle electronics that provide the corresponding data. Moreover, degradation phenomena, such as brake disc wear or slight plastic deformations of parking lock pawl or parking lock wheel, are not sufficiently indicated, and therefore the actuating precision of the parking brake or auxiliary brake decreases during the course of vehicle operation.